// 精准计算功能，用于解决JavaScript浮点数运算精度不准确的问题
module.exports = {
    add: function(arg1, arg2) {
      var r1, r2, m
      try {
        r1 = arg1.toString().split('.')[1].length
      } catch (e) {
        r1 = 0
      }
      try {
        r2 = arg2.toString().split('.')[1].length
      } catch (e) {
        r2 = 0
      }
      m = Math.pow(10, Math.max(r1, r2))
      return (arg1 * m + arg2 * m) / m
    },
    sub: function(arg1, arg2) {
      var r1, r2, m, n
      try {
        r1 = arg1.toString().split('.')[1].length
      } catch (e) {
        r1 = 0
      }
      try {
        r2 = arg2.toString().split('.')[1].length
      } catch (e) {
        r2 = 0
      }
      m = Math.pow(10, Math.max(r1, r2))
      // 动态控制精度长度
      n = (r1 >= r2) ? r1 : r2
      return ((arg1 * m - arg2 * m) / m).toFixed(n)
    },
    mul: function(arg1, arg2) {
      var m = 0,
        s1 = arg1.toString(),
        s2 = arg2.toString()
      try {
        m += s1.split('.')[1].length
      } catch (e) {}
      try {
        m += s2.split('.')[1].length
      } catch (e) {}
      return Number(s1.replace('.', '')) * Number(s2.replace('.', '')) / Math.pow(10, m)
    },
    div: function(arg1, arg2) {
      var t1 = 0,
        t2 = 0,
        r1, r2
      try {
        t1 = arg1.toString().split('.')[1].length
      } catch (e) {}
      try {
        t2 = arg2.toString().split('.')[1].length
      } catch (e) {}
  
      r1 = Number(arg1.toString().replace('.', ''))
      r2 = Number(arg2.toString().replace('.', ''))
      return (r1 / r2) * Math.pow(10, t2 - t1)
    }
  }